1. Field of the Invention
The present invention relates to the field of variable speed mechanical power transmission systems, which systems include a mechanism for the transmission of power between grooved pulleys wherein the transmission system includes at least one endless belt having a plurality of transverse links positioned thereon. Such systems include flexible elements, or belts, that operate by dry adherence, that is, without externally provided lubrication between the grooved pulleys. The belt may include an interior V-shaped endless loop with a plurality of thrust links positioned thereon. The grooved pulleys may have fixed cheeks or flanges, or also, as is often used in variable speed transmissions, the pulleys may have movable cheeks or flanges. Both types of pulleys and/or transmissions are encountered in automotive applications and on agricultural and industrial equipment.
The variable feature of such systems is achieved by relative displacement between the pairs of cheeks, or flanges, of one or more pulleys of the system. Such systems may employ drive and/or receiver pulleys that have conical belt engagement surfaces to provide variable diameters thereof. Such systems may operate by dry mechanical adherence. The power transmission element in the form of a flexible belt transfers mechanical power between the pulleys of such transmission systems. The belt includes an interior endless loop.
2. Background Information
This application claims priority from French Patent Application No. 9 004 162. French Patent Application No. 9 004 162, in turn, is a Certificate of Continuation filed pursuant to a French principal application filed Jan. 11, 1988. This French principal application filed Jan. 11, 1988 is identified as French Patent Publication No. 2 625 783 and French Application Serial No. 88 00244 ("FR '244") and is entitled "Transmission Mechanism for Infinitely Variable Transmission With Transverse Thrust Links and Flexible Core, Operating by Dry Friction." U.S. Pat. No. 4,968,288, issued Nov. 6, 1990, ("U.S. '288") claims priority from FR '244.
The list of prior art described in U.S. '288 can be supplemented by the addition of West German Patent Publication No. 2,557,724. West German Patent Publication No. 2,557,724, assigned to Hans Heynau GmbH, discloses links of transmission elements having matching contact surfaces between the links. The matching contact surfaces are provided to ensure transverse integrity, solidarity, adherence and/or contact among the links.
French Patent Publication No. 2,540,953, assigned to Regie Nationale Des Usines Renault et Compagnie Des Produits Industriels De L'Ouest, discloses a transmission system having links. The links have centering pins and matching holes to ensure the transverse integrity, solidarity, adherence and/or contact between staples and/or riders of the system. Characteristics of this transmission system include the configuration of the contact surface of the links and the configuration of the band that forms a flexible core of the system.
European Patent Publication No. 0,073,962, assigned to Nissan Motor Company, Limited, discloses staples and/or riders, formed by blocks that are positioned sequentially in a first position and a second position relative to an endless band, or belt. The second position is rotated 180.degree. from the first position about the axis. The axis is perpendicular to the longitudinal plane defined by the endless band. The blocks are equipped with pins and holes. The blocks are relatively positioned such that the pins of one block fit within the holes of an adjacent block.
U.S. Pat. No. 4,433,965 to Hattori is assigned to Nippondenso Co. Ltd., and U.S. Pat. No. 4,610,648 to Miranti is assigned to Dayco Corporation. These two U.S. patents disclose transmission systems having flexible cores. The flexible cores include flat belts that support links. The links are constructed of modified polymers or composites and are reinforced, as necessary, with short fibers.
In summary, all of the above-cited patent documents relate, essentially, to a flexible belt having a flexible core. The flexible core being a flat band, strip, or super-imposition or stack of metal bands.
In actual use, all of the devices disclosed in the above-recited patent documents are extremely unstable when the power belt is traveling in the straight line portion of its trajectory, such as between two pulleys. The instability is the result of thrust on and/or through the belt. Such thrust is exerted by reciprocal contact between the aligned links of the belt. This problem of instability was already known at the time of the filing of FR '244. The particular embodiment of the invention shown in FIG. 7 of FR '244 and the subject of Claim 22 of FR '244 attempted to remedy such instability.
During actual use of the device of FIG. 7 of FR '244, however, it was determined that even the coincidence between the imaginary, or predicted, original line of travel of the thrust links and the travel of the neutral fiber of the loop did not ensure stability of the device. Therefore, the stability of the device may be inadequate when significant and high mechanical power must be transmitted through the device.